1. Field of the Invention
The present invention relates generally to an apparatus for taking blood samples, and more specifically, to such apparatus comprising:
an elongate lancet portion defining an axis and having a first and second terminal end, the first lancet portion terminal end being provided with a knob section and the second lancet portion terminal end being provided with a protruding lancet cutting edge section; PA1 an elongate sleeve portion for receiving and axially guiding the lancet portion, the sleeve portion having a first and a second terminal end, the first sleeve portion terminal end being provided with a flange; and PA1 a mechanical axial obstacle arranged between the lancet portion and the sleeve portion, the mechanical axial obstacle being adapted to the overcome upon application of a predetermined amount of axial force between the lancet portion and the sleeve portion,
wherein the lancet portion, in a first operational position, is axially held within the sleeve portion with the knob section being at a first axial distance from the flange and the protruding lancet cutting edge section being entirely enclosed by the second sleeve portion terminal end, whereas, in a second operational position, the lancet portion is axially held within the sleeve portion with said knob section being at a second axial distance from the flange and the protruding lancet cutting edge section protruding from the second sleeve portion terminal end, the mechanical axial obstacle acting as an axial stop between the lancet portion and the sleeve portion, whereas upon application of the predetermined amount of axial force between the lancet portion and the sleeve portion the mechanical axial obstacle is overcome, resulting in an abrupt transition from the first to the second operational position.
2. Brief Description of the Prior Art
An apparatus of the afore-mentioned kind has been known from U.S. Pat. No. specifications 4,676,244 and 4, 712,548 and 4,738,261.
This prior art apparatus for taking blood samples has a sleeve portion being provided with a through bore. An axial stop extends radially into the through bore. The lancet portion, in contrast, is provided with a peripheral bulge such that the lancet portion, in the first operational position, rests on the axial stop.
If the lancet portion and the sleeve portion are axially pressed together, then the mechanical resistance as established by the annular bulge of the lancet portion and resting on the radial stop within the through bore of the sleeve portion is overcome. The axial force exerted on the lancet portion is, thus, abruptly set free so that the lancet portion, having previously been entirely enclosed within the sleeve portion, now suddenly shoots to the opposite end of the sleeve portion. If the apparatus is applied, e.g. on the finger tip of a patient, the lancet portion will intrude into the finger tip and patient blood will exit therefrom. The blood may then be taken for a subsequent medical laboratory examination.
The prior art apparatus is manufactured in an injection molding machine tool as one piece. For that purpose the design is such that the lancet portion is molded to annular flange of the sleeve portion such that the lancet cutting edge section extends into the annular flange of the sleeve portion and is, hence, embedded in the annular flange plastic material. In such a way the lancet cutting edge section is kept sterile prior to the use of the blood taking apparatus because it is entirely surrounded by plastic material.
When a blood sample is to be taken, one has, therefore, to first manually separate the lancet portion from the sleeve portion and to then draw the lancet cutting edge section out of the annular flange. The lancet portion must then be fitted into the sleeve portion by inserting a circular cylindrical section of the lancet portion into the through bore of the sleeve portion until the annular bulge, mentioned above, rests on the axial stop.
Blood sample taking apparatuses of the afore-mentioned kind are frequently used by patients themselves, i.e. by medical laymen, for example by patients suffering from diabetes who have to carry out blood controls at their home in regular time intervals. With this kind of people one cannot always be sure that the required manipulations are made with the necessary precision and care.
Therefore, the prior art apparatus has some essential drawbacks.
First of all, the prior art apparatus has the disadvantage that the axial stop to be overcome has the shape of an annular bulge together with a radial stop so that the through bore outside of the radial stop area has a larger diameter, namely the diameter of the annular bulge. Therefore, the lancet portion cannot be exactly, i.e. linearly, be guided within the sleeve portion.
Another disadvantage of the prior art apparatus is that it is designed for one intrusion depth of the lancet cutting edge section only. However, for different patients the skin thickness in the area where the blood sample shall be taken, may be different, too, so that if the intrusion depth is set as a fixed value, this might result in a substantial injury for a patient having a relatively thin skin whereas for other patients having a relatively thick skin the intrusion depth might be unsufficient.
Moreover, the prior art apparatus has the disadvantage that its manipulation requires a certain skill, in particular during the preparation of the apparatus when the lancet portion is to be separated from the sleeve portion and the two portions have to be assembled together. During such manipulations it might happen that inadverdently the lancet portion falls down and the lancet cutting edge section will be contaminated. Further, it cannot be excluded that the patient will be injured during the assembling of the two portions together when the lancet cutting edge section is uncautiously handled. Moreover, it is a certain disadvantage that the patient during the assembling of the two portions together visually becomes aware of the lancet cutting edge section which might have disadvantageous psychological effects.
It is, therefore, an object underlying the invention to improve a blood sample taking apparatus of the kind mentioned at the outset such that the afore-mentioned disadvantages are overcome. In particular, the apparatus shall be improved such that the two portions may be exactly guided on each other. Further, it shall be possible to exactly preset the lancet cutting edge section intrusion depth at selected values. Moreover, difficult manipulations of the apparatus prior to its actual use shall be avoided. Moreover, any contamination of the lancet cutting edge section shall be made impossible and psychological drawbacks with respect to the patient shall be avoided.